She hasn't even been confirmed by the Senate yet! Apparently, Biden doesn't care about this little thing called the Constitution.
https://conservativefiringline.com/biden-attempts-to-add-acting-secretary-of-labor-julie-su-to-line-of-succession-to-president/
Biden Attempts to Add Acting Secretary of Labor Julie Su to Line of Succession to President ⋆ Conservative Firing Line
Julie Su is the Acting Secretary of Labor, but has not been confirmed by the Senate. Biden has placed her in the line of succession.
https://conservativefiringline.com/biden-attempts-to-add-acting-secretary-of-labor-julie-su-to-line-of-succession-to-president/